Computerized spiral analysis using the iPad

Abstract

Background: Digital analysis of writing and drawing has become a valuable research and clinical tool for the study of upper limb motor dysfunction in patients with essential tremor, Parkinson's disease, dystonia, and related disorders. We developed a validated method of computerized spiral analysis of hand-drawn Archimedean spirals that provides insight into movement dynamics beyond subjective visual assessment using a Wacom graphics tablet. While the Wacom tablet method provides robust data, more widely available mobile technology platforms exist.

New method: We introduce a novel adaptation of the Wacom-based method for the collection of hand-drawn kinematic data using an Apple iPad. This iPad-based system is stand-alone, easy-to-use, can capture drawing data with either a finger or capacitive stylus, is precise, and potentially ubiquitous.

Results: The iPad-based system acquires position and time data that is fully compatible with our original spiral analysis program. All of the important indices including degree of severity, speed, presence of tremor, tremor amplitude, tremor frequency, variability of pressure, and tightness are calculated from the digital spiral data, which the application is able to transmit.

Comparison with existing method: While the iPad method is limited by current touch screen technology, it does collect data with acceptable congruence compared to the current Wacom-based method while providing the advantages of accessibility and ease of use.

Conclusions: The iPad is capable of capturing precise digital spiral data for analysis of motor dysfunction while also providing a convenient, easy-to-use modality in clinics and potentially at home.

Keywords: Computerized spiral analysis; Graphonomics; Movement disorders; Telemedicine; iPad.

Figure 1

iPad Application Graphical User Interface (GUI). A simple GUI provides the patient with a 10×10 cm workspace in which to draw a spiral. The interface allows the spiral data to be cleared from the device, saved, or sent via email to be analyzed. Button and label layout has been optimized to reduce spiral acquisition time. The application can generate a sample spiral with a radius of 5 cm drawn at a rate of one revolution per second as a demonstration. The patient then draws their own spiral freehand, shown in this figure, attempting to emulate the computer generated spiral as closely as possible.

Figure 2

Graphical representation of spiral data acquired from one control and one ET patient on both the iPad and Wacom tablet. Column A contains data from a control on the iPad and Column B contains data from the same control patient on the Wacom. Column C contains data from an ET patient on the iPad and Column D contains data from the same patient on the Wacom. Rows contain data as follows: 1. Raw spiral graphic; 2. Radius-angle transforms; 3. Spiral widths; 4. Tremor axes; 5. Time vs. trace; 6. Speed vs. angle.